<!DOCTYPE html>
<html>
<head>
<style>
    .outer {
        transform-style: preserve-3d;
        width: 200px;
        height: 200px;
        opacity: 0.7;
    }
    .inner {
        top: 50%;
        transform: translateY(-50%);
        background-color: green;
        position:relative;
        width: 200px;
        height: 200px;
    }
</style>
</head>
<body>

<div id="outer" class="outer">
    <div class="inner">
    </div>
</div>
</body>
</html>

